Swelling with a Near-Theta Solvent as a Means to Modify the Properties of Polymer Thin Films
Andrew Clough, Mithun Chowdhury, Kaiwan Jahanshahi, Günter Reiter, Ophelia K.C. Tsui. Macromolecules 45, 6196−6200 (2012)
Abstract
The effect of swelling with a near-theta solvent on the thermal expansion and dewetting behavior of polystyrene films is studied. Spin-coating a film from a near-theta solvent has been found to produce a chain conformation further from equilibrium than that by spin-coating from a good solvent. Swelling a film with a near-theta solvent is expected to produce a similar effect. We find that there is a significant thermal contraction in the films swelled with decalin -- a theta-solvent of polystyrene at 16 °C. The size of this thermal contraction decreases as the sample is aged, and appears to be due to the solvent used and not the solvent quality. On the other hand, the effect of aging on the dewetting behavior is seen to depend on the solvent quality similar to that for the films spun-cast from a near-theta solvent, with an offset attributable to the swelling conditions and initial chain conformation of the film. Our result suggests that the thermal expansion is not nearly as sensitive to the film’s chain conformation as is the dewetting behavior.